Sweet Potatoes au Gratin

Sweet potatoes au gratin is one of those dishes that’s indulgent but worth it. I love this dish because it’s decadent and savory from the gruyere and parmesan and balanced out by the sweetness of the sweet potatoes. The nutmeg, sage, and thyme make it deliciously fragrant as well. I also love making potato gratin if I’m in the mood for just savory. I would make this for a holiday dinner (Thanksgiving for example!) or a special night in.

Notes on Ingredients and substitutions

• Cheese: traditional gratin is made with gruyere but feel free to chose a combination of cheese you like. You could use Emmental, a sharp Cheddar or Blue Cheese for example. These cheeses can complement sweet potato au gratin nicely.
• Herbs: we’re using sage and thyme in the recipe but you could also use rosemary instead.
• Spices: Nutmeg is must for this dish, and a little goes a long way. Alternatively, you could use a bit of cinnamon too for a unique twist on sweet potato au gratin.

*See recipe card for full list of ingredients and quantities

How to Make this Recipe

1. Preheat oven to 400°F (200°C)

2. Slice potatoes with the mandoline slicer with ⅛ inch thickness. This will ensure the right texture for your sweet potato au gratin.

3. In a small saucepan, add the heavy cream, thyme leaves, chopped sage, grated garlic and nutmeg on medium heat until it simmers.

4. Add one even layer of potatoes on the baking dish, season the layer with salt, pepper and the 2 cheeses. Repeat 3-4 more times. Pour the cream mixture and add the remaining cheese. This layering technique is key for an excellent sweet potato au gratin.

5. Bake for 40 minutes using the middle rack until you have tender potatoes (you can check this with a fork). Then turn on your broiler and broil for 5-7 minutes until the top layer becomes golden brown. Let it cool for 10 mins before serving.

Storage Tips

• You can make this dish a day ahead. Bring it to room temperature and set the oven temperature to 350F, bake for about 20 minutes or until it's hot. This makes sweet potato au gratin great for meal prepping.
• To store, cover the baking dish in foil and store in the refrigerator for up to 4 days. This will keep your sweet potato au gratin fresh.

Print Recipe

Sweet Potato Gratin

Isabelle Lopez

This Sweet Potatoes au Gratin recipe features thinly sliced sweet potatoes layered with rich cream, aromatic herbs, and a blend of melted cheeses. Baked to golden perfection with a crisp, bubbly top, it's a comforting and elegant side dish perfect for any dinner gathering. The tender, creamy potatoes infused with garlic, thyme, and sage make each bite a delicious treat.

Prep Time20 minutes mins

Cook Time48 minutes mins

1x2x3x

Course: Side Dish

Cuisine: American, French

Keyword: Gratin Dauphinois, Potatoes Au Gratin, sweet potato gratin

Servings: 6 people

Equipment

• 1 mandoline
• small saucepan
• baking dish
• Microplane

Ingredients

• 2-2.5 lbs sweet potatoes
• 1 ¼ cups heavy cream
• kosher salt
• black pepper
• 1 cup parmesan - 3-4 oz
• 2 cup gruyere grated - 6-8 oz
• pinch nutmeg
• 2 cloves garlic grated
• 2 teaspoons fresh thyme leaves chopped
• 2 teaspoons fresh sage chopped

Instructions

• Preheat oven to 400F.
• Slice potatoes with the mandoline slicer with ⅛ inch thickness.
• In a small saucepan, add the heavy cream, thyme leaves, chopped sage, grated garlic and nutmeg on medium heat until it simmers.
• Add one even layer of potatoes on the baking dish, season the layer with salt, pepper and the 2 cheeses. Repeat 3-4 more times. Pour the cream mixture and add the remaining cheese.
• Bake for 40 minutes using the middle rack until you have tender potatoes (you can check this with a fork). Then turn on your broiler and broil for 5-7 minutes until the top layer becomes golden brown. Let it cool for 10 mins before serving.

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